ardor vs dullness

ardor

noun
  • Intense heat. 

  • Great warmth of feeling; fervor; passion. 

  • Spirit; enthusiasm; passion. 

dullness

noun
  • The quality of not perceiving or kenning things distinctly. 

  • The quality of being uninteresting; boring; humorless or irksome. 

  • The quality of being slow of understanding things; stupidity. 

  • Lack of interest or excitement. 

  • The lack of visual brilliance; want of sheen. 

  • bluntness. 

How often have the words ardor and dullness occurred in a corpus of books? (source: Google Ngram Viewer )